Gas extraction structure for mold

ABSTRACT

A gas extraction structure ( 40 ) is used for a mold apparatus ( 100 ). The gas extraction structure connects with a mold cavity ( 300 ). The mold cavity includes an end portion of a plastic injection path ( 210 ). The gas extraction structure includes a gas vent ( 490 ), a gas vent pin ( 49 ), and a support structure ( 40 ). The gas vent communicates with the end portion of the plastic injection path. The gas vent pin received in the gas vent. The support structure is fixed with the gas vent pin and brings the gas vent pin to move in the gas vent.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to gas extraction devices for molds and, particularly, to a gas extraction structure for a plastic molding mold capable of sufficiently removing air and reaction product gases from a cavity of a mold.

2. Discussion of the Related Art

Most products made of polymers or other plastics are typically created using injection molds. During a typical injection molding process, a molten material is injected into a mold cavity via a runner. The molten material in the cavity is cooled to form the molded product.

However, the molten material usually contains air or reaction product gases. If the gas in the cavity is not extracted, the gas might affect the formation of the final product. In a conventional injection mold apparatus, a means of extracting gas uses a plurality of venting holes defined at a parting plane between two separable sections of the injection mold. Alternatively, the gas is exhausted through a gap between an ejector pin and an ejector pin hole. However, these conventional venting methods create surface burrs on the molded product.

Therefore, an improved gas extraction structure is desired in order to overcome the above-described problems.

SUMMARY

One embodiment of a gas extraction structure is configured to connect to a mold cavity. The mold cavity includes an end portion of a path of filing material. The gas extraction structure includes a gas vent, a gas vent pin, and a support structure. The gas vent is configured to communicate with the end portion of the material injection path. The gas vent pin is movably received in the gas vent. The support structure is attached to an end of the gas vent pin that is configured to be distal from the end portion of the material injection path. The support structure is configured to drive the gas vent pin to a position where an opposite end of the gas vent pin is adjacent to the end portion of the material injection path.

Other advantages and novel features of the present gas extraction structure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present gas extraction structure. Moreover, in the drawing, like reference numerals designate corresponding parts.

FIG. 1 is a partial cross-sectional view of a mold apparatus including a gas extraction structure in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

Referring now to the drawing in detail, FIG. 1 shows a gas extraction structure for a mold in accordance with one embodiment of the present invention. In an exemplary application, the gas extraction structure is incorporated in an injection mold apparatus 100.

The injection mold apparatus 100 includes an upper mold 10, a lower mold 20, an ejector structure 30, and a gas extraction structure 40. The upper mold 10 and the lower mold 20 may be separable from each other. When the upper and lower molds 10, 20 are engaged together, a parting plane 120 is formed between them.

The upper mold 10 includes an upper fixed plate 12, an upper mold part 14, and an upper mold core 16. The upper fixed plate 12, the upper mold part 14, and the upper mold core 16 are fixed together by means of screws, so that the upper mold 10 forms a fixed side of the injection mold apparatus 100.

The upper fixed plate 12 is substantially square, and may be fixedly attached in the injection mold apparatus 100. The upper fixed plate 12 defines an opening 122 in a central area thereof. A positioning ring 124 is engaged in the opening 122. The upper mold part 14 defines a recess, and the upper mold core 16 is engaged in the recess. The upper mold part 14 and the upper mold core 16 respectively define a common through hole 140 in central areas thereof. The through hole 140 communicates with the opening 122 of the upper mold core 16. A bush 126 is inserted into the positioning ring 124, so that a bottom end of the bush 126 is received in the through hole 140, and a top end of the bush 126 is received in the positioning ring 124. The bush 126 has a runner 128 defined in a central area thereof. The bush 126 is used seating a nozzle (not shown) of the injector mold apparatus 100. The positioning ring 124 may help the nozzle align with the runner 128 of the bush 126.

The lower mold 20 includes a lower fixed plate 22, two spaced blocks 24, a support plate 26, a lower mold part 28, and a lower mold core 29. The lower fixed plate 22, the spaced blocks 24, the support plate 26, the lower mold part 28 and the lower mold core 29 are fixed together by means of screws, so that the lower mold 20 forms a movable side of the injection mold apparatus 100.

The lower fixed plate 22 is substantially square, and is fixed to a movable disk (not shown) of the injection mold apparatus 100. Each spaced block 24 is substantially rectangular, and is supported on one of two ends of the lower fixed plate 22. The spaced blocks 24 are of a height sufficient to provide a desired distance between the lower fixed plate 22 and the support plate 26. The support plate 26 is fixed on the two spaced blocks 24. The lower mold part 28 is fixed on the support plate 26. The lower mold part 28 defines a recess, and the lower mold core 29 is engaged in the recess. When the upper and lower mold cores 16, 29 are engaged together, they cooperatively form a mold cavity 300 therebetween. The runner 128 communicates with the mold cavity 300 so that molten material such as molten plastic may flow along the runner 128 into the mold cavity 300. The support plate 26, the lower mold part 28 and the lower mold core 29 cooperatively define a plurality of common through holes 360. The support plate 26, the lower mold part 28 and the lower mold core 29 together cooperatively a common gas vent 490.

The ejector structure 30 is movably positioned above the lower fixed plate 22, between the two spaced blocks 24. The ejector structure 30 includes a first ejector plate 32, a second ejector plate 34, and a plurality of ejector pins 36.

The first ejector plate 32 defines a plurality of stepped holes 320. Each ejector pin 36 extends through a corresponding stepped hole 320, and is movably received in a corresponding through hole 360. The second ejector plate 34 is fixed on a bottom side of the first ejector plate 32. Thus one end of each ejector pin 36 is locked into the corresponding stepped hole 320 by the second ejector plate 34, so as to fix all the ejector pins 36 in the ejector structure 30.

The gas extraction structure 40 includes a first support plate 42, a second support plate 44, two springs 46, two rods 48, and a gas vent pin 49.

The first support plate 42 and the second support plate 44 are positioned between the two spaced blocks 24, under the second ejector plate 34. The first support plate 42 and the second support plate 44 are fixed together. The second ejector plate 34 defines two guide holes 480. A diameter of the guide holes 480 is slightly larger than that of the rods 48. A bottom end of each rod 48 is fixed to the first support plate 42, and a top end of each rod 48 is movably received in a corresponding guide hole 480. A portion of each rod 48 below the second ejector plate 34 is surrounded by a corresponding spring 46. A diameter of each spring 46 is larger than that of each guide hole 480. Accordingly, the springs 46 resist both the second ejector plate 34 and the first support plate 42. If the first support plate 42 and the second support plate 44 are pressed upward, the first support plate 42 and the second support plate 44 move together relative to the first ejector plate 32 and the second ejector plate 34, with the rods 48 sliding along the guide holes 480.

The mold cavity 300 has a distal end portion 210 of a plastic injection path. That is, when the molten plastic is injected into the mold cavity 300, the molten plastic follows a path within the mold cavity 300, and the distal end portion 210 is at the end of the path. The gas vent pin 49 is received in the gas vent 490. A connecting aperture 492 connects the gas vent 490 with the end portion 210 of the mold cavity 300. A diameter of the connecting aperture 492 is smaller than that of the gas vent 490, thereby forming a step where the connecting aperture 492 adjoins the gas vent 490. A diameter of the gas vent pin 49 is smaller than that of the gas vent 490, and slightly smaller than that of the connecting aperture 492, so that the gas vent pin 49 can be movably received in the gas vent 490 and the connecting aperture 492. A gap between the wall of the gas vent 490 and the gas vent pin 49 needs to be of sufficient size so that most of unwanted air or reaction product gases can be vented therebetween.

In use, before the molten material (such as molten plastic or molten resin) is injected into the mold cavity 300, the mold cavity 300 typically has air inside. The first support plate 42 and the second support plate 44 are in an original passive position relative to the first and second ejector pin plates 32, 34. In this position, the gas vent pin 49 is farthest from the end portion 210. When the molten plastic is injected, the molten plastic firstly injects from the nozzle of the mold apparatus 100. Then, the molten plastic flows into the runner 128 of the bush 126. Because the runner 128 communicates with the mold cavity 300, the molten plastic further flows into the mold cavity 300. During this filling process, the molten plastic brings air and reaction product gases into the mold cavity 300. While the molten plastic continues to fill the mold cavity 300, a part of the air and reaction product gases in the mold cavity 300 is vented through the gas vent 490 via the connecting aperture 492. After about 95 percent of the molten plastic has been injected, the first support plate 42 and the second support plate 44 are pushed upward by a driving structure (not shown) of the mold apparatus 100. Therefore, the gas vent pin 49 moves upward until a top surface of the gas vent pin 49 is substantially coplanar with a corresponding part of the lower mold core 29 at a top of the connecting aperture 492. During this time, the molten plastics continues to be injected into the mold cavity 300, and a remaining amount of the air and reaction product gases is driven into a small gap between the gas vent pin 49 and a wall of the connecting aperture 492 and vented out through the gas vent 490. Once the molten plastic has filled the whole mold cavity 300, all of the remaining air and reaction product gases has been completely vented from the mold cavity 300 into the gap and out through the gas vent 490. At the same time, the gas vent pin 49 encloses the end portion 210 so that the molten plastic cannot flow in the connecting aperture 492.

Finally, after cooling of the molten plastic, the upper mold 20 is separated from the lower mold 10. Then the first ejector pin plate 32, the second ejector pin plate 34, the first support plate 42 and the second support plate 44 are moved together by a back rod (not shown) of the injection mold apparatus 100 so as to make the ejector pins 36 and the gas vent pin 49 move up and push the solidified plastic piece. Thus, the molded product is pushed out from engagement with the lower mold core 29. When the driving force by the back rod is released, the springs 48 rebound, and the first support plate 42 and the second support plate 44 can return to their original passive position relative to the first and second ejector pin plates 32, 34. Typically, when the solidified plastic piece is pushed out from engagement with the lower mold core 29, no molten plastic may enter the gap because the gap is sufficiently small. In such cases, with the top surface of the gas vent pin 49 being coplanar with the part of the lower mold core 29 at the top of the connecting aperture 492, the surface of the molded product at this location only has a small mark from the gas vent pin 49. Because a size of the mark is small such that a surface of the molded product at the point of the end portion 210 cannot be effected. The mark is typically formed on an inside surface of the molded product. Therefore, the mark does not also effect the work surface of the molded product.

As described above, the gas vent pin 49 is configured to allow the air and reaction product gases in the mold cavity 300 to vent out therefrom, as well as to help eject the molded product. A main advantage of the gas extraction structure 40 is that the molded product not only has good stiffness in a central portion thereof due to the absence of air and reaction product gases during formation, but also may achieve a good appearance. In addition, the gas extraction structure 40 is simple in structure. The gas extraction structure 40 may greatly improve the product quality at relatively little cost.

The above-described gas extraction structure 40 can be used with other kinds of molding apparatuses besides the injection mold apparatus 100 illustrated, or with other kinds of apparatuses that need a gas extraction structure. The products formed can have good mechanical strength as well as a smooth, attractive appearance.

It is believed that the present embodiment and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention. 

1. A gas extraction structure for a mold apparatus, the gas extraction structure configured to be connected to a mold cavity, the mold cavity including an end portion of a material injection path, the gas extraction structure comprising: a gas vent configured to communicate with the end portion of the material injection path; a gas vent pin movably received in the gas vent; and a support structure attached to an end of the gas vent pin that is configured to be distal from the end portion of the material injection path, the support structure configured to drive the gas vent pin to a position where an opposite end of the gas vent pin is adjacent to the end portion of the material injection path.
 2. The gas extraction structure as claimed in claim 1, wherein the gas vent includes a connecting aperture, a diameter of the connecting aperture is smaller than that of a main portion of the gas vent, and the connecting aperture is configured to intercommunicate the main portion of the gas vent and the end portion of the material injection path.
 3. The gas extraction structure as claimed in claim 2, wherein a diameter of the gas vent pin is slightly smaller than that of the connecting aperture, and smaller than that of the main portion of the gas vent.
 4. The gas extraction structure as claimed in claim 1, wherein the support structure includes a support plate, and the gas vent pin is attached to the support plate.
 5. The gas extraction structure as claimed in claim 1, wherein the support structure includes a first support plate and a second support plate, and the first support plate and the second support plate cooperatively support the gas vent pin.
 6. A mold apparatus comprising: an upper mold; a lower mold cooperating with the upper mold to define a mold cavity therebetween, wherein the mold cavity includes an end portion of a material injection path; a gas vent communicating with the end portion of the material injection path; a gas vent pin movably received in the gas vent; and a support structure attached to the gas vent pin and configured to drive to the gas vent pin to move in the gas vent to a position where an end of the gas vent pin is adjacent to the end portion of the material injection path.
 7. The mold apparatus as claimed in claim 6, wherein the gas vent includes a connecting aperture, a diameter of the connecting aperture is smaller than that of the gas vent, and the connecting aperture connects the gas vent and the mold cavity.
 8. The mold apparatus as claimed in claim 7, wherein a diameter of the gas vent pin is slightly smaller than that of the connecting aperture, and smaller than that of the main portion of the gas vent.
 9. The mold apparatus as claimed in claim 6, wherein the support structure includes a support plate, and the gas vent pin is attached to the support plate.
 10. The mold apparatus as claimed in claim 6, wherein the support structure includes a first support plate and a second support plate, the first support plate and the second support plate together support the gas vent pin.
 11. The mold apparatus as claimed in claim 10, further comprising an ejector structure positioned under the lower mold.
 12. The mold apparatus as claimed in claim 11, wherein the ejector structure includes a first ejector plate, a second ejector plate, and a plurality of ejector pins, and the ejector pins are attached on the first ejector plate and the second ejector plate.
 13. The mold apparatus as claimed in claim 12, wherein the support structure further comprises at least one rod, and the at least one rod is positioned generally between the first support plate and the second ejector plate.
 14. The mold apparatus as claimed in claim 13, wherein the second ejector plate defines at least one guide hole, and one end of the at least one rod is movably received in the at least one guide hole.
 15. The mold apparatus as claimed in claim 14, further comprising at least one spring, wherein the at least one spring is located around the at least one rod between the first support plate and the second ejector plate.
 16. A gas extraction structure comprising: a mold cavity having an end portion of a material injection path; a gas vent generally adjacent to the end portion of the material injection path; a connecting aperture interconnecting the gas vent and the end portion; a pin movably received in the gas vent; and a support structure fixed to the gas vent pin distal from the connecting aperture, the support structure configured to drive the pin between a first position in which the connecting aperture is clear and a second position in which the pin occupies the connecting aperture and is adjacent to the end portion of the material injection path.
 17. The gas extraction structure as claimed in claim 16, wherein a diameter of the gas vent is larger than that of the pin, and a diameter of the pin is substantially equal to that of the connecting aperture.
 18. The gas extraction structure as claimed in claim 16, wherein the support structure includes a first support plate and a second support plate, the first support plate and the second support plate cooperatively support the pin.
 19. The gas extraction structure as claimed in claim 16, wherein the support structure is configured to drive the pin from the first position to the second position when the mold cavity has been injected with molten material to about 95 percent of a capacity of the mold cavity.
 20. The gas extraction structure as claimed in claim 16, wherein the support structure is further configured to drive the pin between the second position and a third position in which the pin has pushed a molded body away from a position corresponding to a position of the mold cavity. 